1. Field of the Invention
This invention relates to an apparatus and method for an image data processing apparatus, and more particularly to an apparatus and method for an image data processing apparatus that is capable of correcting dots of bit-mapped image data with a relatively small-sized memory capacity.
2. Discussion of the Background
An image data processing apparatus has been developed which is capable of correcting jagged lines formed in bit-mapped image data to improve image quality with a minimal memory for storing correct data. One example of such a technique is disclosed in U.S. Pat. No. 5,327,260. This disclosed technique uses a CPU (central processing unit) or the like to determine which dots need a correction and what correct data is needed. More specifically, the CPU recognizes a figure of a line segment formed between black and white dot areas relative to each dot of interest included in bit-mapped image data. The CPU converts the recognized figure of the line segment into a n-bit code and determines whether the dot of interest needs a correction, using at least a part of the n-bit code. If correction is needed, the CPU performs the correction in accordance with the n-bit code.
In addition, the image data processing apparatus having the above-described dot correction technique includes a data window, a pattern recognition unit, a determining unit, and a correction data memory. The data window captures a dot of interest and surrounding dots in the bit-mapped image data. The pattern recognition unit recognizes a figure of a line segment which is formed between black and white dot areas relative to the dot of interest in the bit-mapped image data. The pattern recognition unit then generates a n-bit code that represents the figure of the recognized line segment relative to the dot of interest. The determining unit determines whether the dot of interest needs the dot correction, using at least a part of the n-bit code. The correct data memory stores a plurality of correct data which are accessed with the n-bit code used as an address code.
The above-described n-bit code includes a plurality of code information elements. One code information element indicates whether the dot of interest is either black or white. Another code information element represents a direction of gradient of the line segment. Another code information element represents a gradient of the line segment. Another code information element indicates a position of a horizontally- or vertically-continued line segment from an edged dot.
The above-configured image data processing apparatus can determine whether a dot of interest under examination needs a correction and performs the correction to the dot according to the generated n-bit code. The apparatus obviates the necessity to store all the potential patterns of a figure of line segment.
When the n-bit code is a 12-bit code, for example, a maximum of 4096 different figures of a line segment can be expressed. However, an actual number of dots which need the correction may be less than the maximum number.